BUG: An MDI child form may not maximize if the child form contains an ActiveX control in Visual Studio .NET 2003 (871045)

WORKAROUND

To work around this problem, use one of the following methods:

Method 1

Modify the code so that you can maximize the child form, and then modify the code so that you can obtain the focus of an inactive child form:

• To maximize a child form, change the code in step 14 of the "More Information" section to the following:

  Dim frm As Form2
  frm = New Form2
  frm.MdiParent = Me
  frm.WindowState = FormWindowState.Maximized
  frm.Show()

  Note The MdiParent property is used to specify that the Form2 form is a child form.
• To obtain the focus of an inactive child form by clicking the client area of the child form, add code to the child form:
  1. In Solution Explorer, right-click the Form2.vb file, and then click View Code.
  2. Locate the following code in the Form2 class:

     Public Class Form2
         Inherits System.Windows.Forms.Form

  3. Add the following code after the code that you located in step 2:

     Private Const WM_MOUSEACTIVATE As Integer = &H21
     
         Protected Overrides Sub WndProc(ByRef m As Message)
             If m.Msg = WM_MOUSEACTIVATE Then
                 Me.Focus()
             End If
             MyBase.WndProc(m)
     End Sub

     The WM_MOUSEACTIVATE message is sent when the pointer is in an inactive window and the user clicks a mouse button. The WndProc method activates the current MDI child form if the WndProc method receives the WM_MOUSEACTIVATE message.

Method 2

Set the MdiParent property and the WindowState property of the child form before you call the InitializeComponent method in the child form. To do this, you must write code that creates a constructor that takes the MdiParent property and the WindowState property as arguments and that creates a form as an MDI child form:

1. In Solution Explorer, right-click the Form2.vb file, and then click View Code.
2. Locate the following code in the Form2 class:

   Public Class Form2
       Inherits System.Windows.Forms.Form

3. Add the following code after the code that you located in step 2:

   Public Sub New(ByVal mdiParent As Form, ByVal initialState As FormWindowState)
           MyBase.New()
   
           Me.MdiParent = mdiParent
           Me.WindowState = initialState
   
           InitializeComponent()
   
   End Sub

   The constructor initializes the MdiParent property of the child form to specify the parent form. The constructor also initializes the WindowState property of the child form before the constructor calls the InitializeComponent method.
4. Change the code in step 14 of the "More Information" section to the following:

   Dim frm As Form2
   frm = New Form2(Me, FormWindowState.Maximized)
   frm.Show()

You must change the code in all the MDI child forms that contain an ActiveX control if you want to work around the problems that the "Symptoms" section mentions.